The present invention relates to a metallizing device for vacuum metallizing arrangements having a vaporizer heated by an electrical heater and a pot for vaporizing added metal and a nozzle element with a nozzle gap allowing the produced metal vapor to exit.
For the metallizing of foils with, for example, aluminum, copper or other metals with a high melting point, usually so-called evaporation boats are arranged in a vacuum chamber which consists of electrically conductive ceramics and through which, for the purpose of vaporizing added metals, an electrical current flows. These evaporation boats, at times, form a pot for the metal to be vaporized through a hollowed out area. For this purpose, the space above the evaporation boats is completely open so that the metal vaporized in them can directly reach a foil guided above the evaporation boats and can be precipitated through condensation. Such open metallizing devices can be used only for metals with a low vapor pressure because only then the vapor rises to the substrate in a manner extensively directed upwardly. Nonetheless, relatively large areas of the coating arrangement can be reached by the vapor and may be contaminated by it. This leads to the point that the arrangement must be shut down and cleaned relatively frequently so that no long, uninterrupted processing times are possible.
There are known metallizing devices for zinc in which a pot with the metal to be vaporized is arranged in a large-volume vaporizer housing. The heating of this pot takes place indirectly by means of heating coils in ceramic elements. The vaporizer housing is covered towards the top by means of a nozzle element in the form of a plate or a strip, wherein the nozzle element has a nozzle gap through which the vapor reaches the foil to be coated. The nozzle gap must be as long as the foil to be coated is wide because the foil is guided across this nozzle gap for the purpose of coating. For this reason, the vaporizer housing must be correspondingly wide and thus of a large volume.
Such large-volume metallizing devices result in a situation where their heating requires more time than the time needed for producing the necessary vacuum in the coating arrangement. Therefore, the metallizing device must at first be locked by a shutter and then heated before the metallizing of the foil can begin. In the case of high rates of evaporation, so much metal is precipitated on the shutter that it can fall off it and close the nozzle gap either entirely or partially. An additional disadvantage of large-volume metallizing arrangements lies in that the adjustment of the rate of evaporation is very slow which is due to the large bulk of such metallizing arrangements and the large mass of metal inside it which is to be vaporized and due to the fact that the temperature in the metallizing device can be measured only indirectly at the outside wall of the heating pipe. With such metallizing arrangements it is also problematic that, due to wear and tear, short maintenance cycles result and insulation errors or plasma ignition occur. Furthermore, the melting of new zinc with the necessary removal of the oxide skin and the handling of liquid zinc is dangerous and time-consuming.
An object of the invention therefore is to construct a metallizing device of the initially mentioned type in such a way that the rate of evaporation can be changed as rapidly as possible and the possibly minimal contaminations are directed through the vaporized metal so that processing times, which are as long as possible, can be realized with the arrangement without resulting in a standstill.